1. Field of the Invention
The invention relates to a method for applying solder to gold, and additionally relates to printed circuit boards having solder applied to gold members on the board by such method.
2. Description of the Prior Art
The current state of the art in electronics often necessitates applying solder to gold. The solder is used, for example, in soldering electrical components such as resistors, capacitors or the like to the gold conductors used in printed circuit boards.
However, due to the high solubility of gold in the tin component of conventional soft solders made of tin-lead, tin-silver, tin-lead-silver, tin-lead-copper, and the like, alloys, pretinned components or connecting leads attached to the components cannot be soldered to the gold conductors without the gold alloying or diffusing into the tin.
Previous attempts to overcome the problem have included using solders having high indium or extremely high lead contents. Yet, high indium solders have a low inherent mechanical strength as well as a reduced resistance to temperature. High lead solders containing extremely elevated levels of lead have also proven inadequate because of the high soldering temperatures which are necessary. These high temperatures may have the effect of damaging the components being soldered as well as enhancing oxidation of the components which become heated as a result of the soldering process.